Thyroid & parathyroid

Papillary thyroid carcinoma

Rare variants

Fibromatosis / fasciitis-like

Editorial Board Member: Andrey Bychkov, M.D., Ph.D.
Editor-in-Chief: Debra L. Zynger, M.D.
Shipra Agarwal, M.D.

Topic Completed: 4 January 2021

Minor changes: 19 January 2021

Copyright: 2003-2021,, Inc.

PubMed Search: Nodular fasciitis-like papillary carcinoma

Shipra Agarwal, M.D.
Page views in 2020: 662
Page views in 2021 to date: 1,200
Cite this page: Agarwal S. Fibromatosis / fasciitis-like. website. Accessed December 3rd, 2021.
Definition / general
  • Rare histological variant of papillary thyroid carcinoma (PTC)
  • Characterized by an abundant stroma resembling nodular fasciitis / fibromatosis / other myofibroblastic proliferative processes
  • First described by Ostrowski as PTC with fibromatosis-like stroma and by Chan et al. as PTC with nodular fasciitis-like stroma (Am J Clin Pathol 1991;95:309)
Essential features
  • Prominent myofibroblastic proliferation histomorphologically similar to fibromatosis or nodular fasciitis of soft tissue
  • Varying proportion of PTC component
  • CTNNB1 (beta catenin) mutation frequent in mesenchymal component
ICD coding
  • ICD-O: 8260/3 - Papillary carcinoma of thyroid
  • ICD-10: C73 - Malignant neoplasm of thyroid gland
  • Either lobe or isthmus of thyroid gland
Clinical features
  • Asymptomatic / palpable firm neck mass (Endocr J 2017;64:1017)
  • May manifest with cervical nodal metastasis or obstructive symptoms
  • Diagnostic workup is similar to any thyroid mass / nodule
    • Ultrasound with fine needle aspiration cytology (FNAC)
    • CT scan may be useful to evaluate extrathyroidal extension and lymph node metastases
  • Final diagnosis is rendered on histopathological examination of resected tumor
    • Accurate diagnosis of PTC with fibromatosis / fasciitis-like stroma is usually not possible on FNAC; however, preoperative recognition of this variant among other PTC variants does not influence treatment decisions (Endocr J 2017;64:1017)
Radiology description
  • Sonography:
    • Similar to classical PTC (Ultrasound Int Open 2018;4:E39)
    • Classified as intermediate or high suspicion nodule
    • Irregular shape
    • Heterogeneous echogenicity
    • Taller than wide sign (85%)
    • Usually lacks microcalcification (76.9%), macrocalcification (> 2 mm) in 31%
    • Mesenchymal component: heterogeneous (62.5%), more hypoechoic (71.4%) than PTC areas; lacks microcalcification
  • Doppler ultrasound:
    • No or mild flow signal (75.0%)
  • Ultrasound elastography:
    • Mesenchymal component: not stiff; more elastic than PTC areas
Radiology images

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Ultrasound elastography

Color doppler ultrasound

Prognostic factors
Case reports
Gross description
Gross images

Images hosted on other servers:

Well demarcated, solid

Fibrotic nodule

Frozen section description
Microscopic (histologic) description
  • Mixed epithelial-mesenchymal tumor
  • Epithelial component:
  • Mesenchymal component:
    • 20 - 95% of tumor area (Endocr J 2017;64:1017, Ultrasound Int Open 2018;4:E39)
    • Myofibroblastic proliferation similar to fibromatosis / nodular fasciitis / other myofibroblastic proliferative processes
    • Fibromatosis type stroma: dense hypocellular collagenous connective tissue
    • Nodular fasciitis-like stroma: edematous, extravasated red blood cells, inflammatory cells; reminiscent of granulation tissue
    • May infiltrate surrounding neck structures
    • May metastasize to lymph nodes along with the epithelial cell component (Endocr J 2017;64:1017)
Microscopic (histologic) images

Contributed by Ayana Suzuki, C.T.

Mixed epithelial-mesenchymal tumor

Fibromatosis type stroma

Beta catenin

Virtual slides

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PTC with fibromatosis type stroma

Cytology description
  • Usually Bethesda V (suspicious for PTC) or VI (diagnostic of PTC) (Endocr J 2017;64:1017)
  • Aspirate may show stromal fragments containing spindle cells in a myxoid background
    • May be misdiagnosed as nonneoplastic or benign / malignant spindle cell neoplasm or anaplastic thyroid carcinoma
  • Aspirate may be biphasic
    • Admixed epithelial and stromal fragments
  • May be hypocellular / unsatisfactory (Mod Pathol 2020;33:1702)
Cytology images

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Stromal fragment

Stromal fragment

Positive stains
Negative stains
Electron microscopy description
  • Collagen fibers in proximity of mesenchymal cells (Mod Pathol 2017;30:236)
  • Abundant rough endoplasmic reticulum
Molecular / cytogenetics description
  • PTC: BRAF V600E mutation most common, rarely NRAS mutation (Mod Pathol 2020;33:1702)
  • Mesenchymal component: CTNNB1 (beta catenin) mutations
  • Absent USP6 gene rearrangement (limited evidence)
Differential diagnosis
Board review style question #1

How is the variant of papillary thyroid carcinoma shown in the image distinct from other variants?

  1. BRAF V600E mutation in epithelial component
  2. EWSR1 fusions
  3. CTNNB1 (beta catenin) mutation in mesenchymal component
  4. HRAS mutation in epithelial component
  5. CTNNB1 (beta catenin) mutation in epithelial component
Board review style answer #1
C. CTNNB1 (beta catenin) mutation in mesenchymal component

CTNNB1 (beta catenin) mutations have been documented in the mesenchymal component of papillary thyroid carcinoma (PTC) with fibromatosis / fasciitis-like stroma. The PTC (epithelial) component of this tumor lacks CTNNB1 mutation; it instead usually harbors BRAF V600E mutation and less commonly HRAS mutation. BRAF and HRAS mutations are, however, not specific for PTC with fibromatosis / fasciitis-like stroma. CTNNB1 mutations are seen in cancer cells of cribriform-morular variant of PTC. EWSR1 gene fusions are a hallmark of Ewing sarcoma.

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Reference: Fibromatosis / fasciitis-like
Board review style question #2
Which of the following is true about papillary thyroid carcinoma with fibromatosis / fasciitis-like stroma?

  1. Aggressive clinical course
  2. Fibromatosis may recur postthyroidectomy
  3. Only the epithelial component can metastasize
  4. Membranous expression of beta catenin in both epithelial and mesenchymal elements
  5. Stroma always mimics desmoid type fibromatosis
Board review style answer #2
B. Fibromatosis may recur postthyroidectomy

Clinical course of papillary thyroid carcinoma (PTC) with fibromatosis / fasciitis-like stroma is usually similar to classical PTC. The tumor is characterized by a prominent myofibroblastic proliferation reminiscent of fibromatosis or nodular fasciitis, hence the name. Stromal component of tumors with fibromatosis-like stroma commonly harbors CTNNB1 (beta catenin) mutation, which on immunohistochemistry is depicted by nuclear positivity and loss of membranous staining. The PTC component retains normal membranous beta catenin immunoreactivity. The tumor is also unique in that the patients can develop recurrence of fibromatosis postthyroidectomy. Metastases can show both mesenchymal and epithelial components similar to the primary tumor.

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Reference: Fibromatosis / fasciitis-like
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